1. Field of the Invention
The present invention relates to a hydrodynamic bearing device that is installed in a spindle motor that is used for hard disk devices and other such magnetic disk devices, optical disk devices, laser scanning devices, and other such information apparatuses, and that rotationally drives a disk, a polygon mirror, or another such rotor in this device.
2. Description of the Related Art
Hydrodynamic bearing devices in which the fluid pressure of an oil or other such lubricant interposed between a shaft and a sleeve is utilized to support these components so as to be relatively rotatable have been proposed in the past as bearings for spindle motors used in various kinds of information apparatuses that rotationally drive a magnetic disk, an optical disk, a magneto optical disk, or another such disk-shaped recording medium, or a polygon mirror or the like.
It is extremely important to design a hydrodynamic bearing device so that the lubricant does not leak out from between the bearing constituent members. Accordingly, there have been numerous proposals related to constitutions in which a communicating path is provided inside the bearing for the purpose of eliminating pressure unevenness within the bearing, and an adhesive is used to fix and seal the members that make up the bearing.
For example, as shown in Patent Documents 1 (Japanese Laid-Open Patent Application 2003-120662), a constitution is disclosed in which, in bonding a sleeve (serving as a bearing member) and a housing member that supports this sleeve, a communicating path is formed between the inner peripheral surface of the housing member and the outer peripheral surface of the sleeve, and an adhesive reservoir extending in the axial direction is formed around this communicating path in the circumferential direction. With this constitution, the adhesive is prevented from working its way into the communicating path by capturing the adhesive in the adhesive reservoir.
With another communicating path constitution, such as that in Patent Documents 2 (Japanese Laid-Open Patent Application 2004-135419), for example, an outer cylinder member is rotatably inserted via a gap at the inner periphery of a sleeve serving as a bearing member, and an inner shaft formed integrally with a rotor hub is inserted and fixed at the inner periphery of this outer cylinder member. Here, a spiral communicating path and an adhesive groove are provided between the inner shaft and the outer cylinder member, and the two are fitted together and fixed after coating the adhesive groove with an adhesive. This prevents the adhesive from entering the communicating path.